One of the most famous melodies of the Gregorian Chant, Dies Irae was traditionally ascribed to Thomas of Celano (d 1260), but now is usually attributed to an unknown Franciscan of that period. The piece is based upon Zep 1:14-16, a reflection upon the final judgment. It was formerly part of the Mass of the Dead and the Office of the Dead. Today it is found in the Liturgia Horarum for the last week of Ordinary time (34th). In placing it there, the emphasis is upon the upcoming Advent season and the Second Coming of Christ. In Diocese of the United States, it is still used in the Office of the Dead and the Feast of All Souls (Nov. 2).

Many have complained about the depressing nature of the opening verses, but while the piece is certainly sobering, there is a note of hope as well later on in the hymn. Judgment, which is eternal, is indeed a fearsome prospect for us sinners, but, as Christians, we also realize we have Christ as our Savior.